Stabilized detergent composition



United States Patent STABILIZED DETERGENT COMPOITION Harry Howard Reynolds, Penns Grove, N. L, and Oliver Yeaton, Cranston, R. 1., assignors to E. I. do Pout de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application January 20, 1954, Serial No. 405,248

6 Claims. (Cl. 252-152) This invention relates to synthetic detergents of the alcohol sulfate type. More particularly, this invention deals with improved synthetic detergent compositions whose principal or active ingredients is a water-soluble salt of a monoaliphatic ester of sulfuric acid of the general formula wherein M is a water-soluble cation such as sodium, potassium, ammonium or diethanol-ammonium, while R is a normal, saturated or unsaturated, alkyl radical of 10 to carbon atoms, for instance dodecyl, cetyl or oleyl, or the radical of a condensation product of such a normal alcohol with not more than 10 units of ethylene oxide.

It is an object of this invention to provide a process for stabilizing detergents of the aforementioned type against discoloration in storage. A further object is to provide a detergent composition whose active principle is a sulfate of the aforementioned type, the composition being characterized by stability against development of objectionable colors or cloudiness upon storage. A still further object is to provide novel detergent compositions of the mentioned type, which are either water-white or else are adapted to be bleached rapidly by the simple act of exposing to actinic light, such as ultraviolet light or daylight. Various additional objects and achievements of this invention will appear as the description proceeds.

Water-soluble alcohol sulfate salts are important commercial wetting agents and detergents. They are now manufactured in large quantities for use in certain cosmetics such as shampoos and cleansing creams. As normally produced at present, these solutions are colored, ranging from pale straw color to dark amber. Some shades are sufficiently light to give sparkling solutions so that the products are acceptable to the cosmetic trade. On storage, however, particularly when exposed to heat and light, all of these products develop color or deepen their initial color, and assume dull, unattractive shades, which are completely unsatisfactory in this field.

Some of this color is believed to be attributable to iron-containing impurities, and some to by-products of the sulfation step. Actually, the chemical nature of the colored components is not definitely known.

We have now found, that color development in compositions of the aforegoing nature can be effectively arrested, if citric acid or water-soluble citrates are added to solutions of said active principles in quantity to create in the product a concentration of citrate ions of from 0.1 to 3.0% by weight, based on the weight of the entire solution.

Moreover, We have found that the effect of the citrate ions can be immensely increased if a water-soluble salt of the group consisting of iron salts and zinc salts be added in quantity suificient, to create in the solution a concentration of metallic ions of this group of from Patented Oct. 2, 1956 0.0005 to 0.01% by weight (based on the weight of the solution). We find that when such metals are present, the effect of the citrate is not merely to arrest the development of objectionable color, but actually to destroy whatever coloration the composition has had to begin with, upon exposure of the solution to daylight.

The aforegoing effect of iron and zinc ions is most astonishing, inasmuch as it is generally assumed that iron impurities are the cause of objectionable colorations in most liquid or pasty compositions of matter. Furthermore, as has already been mentioned, the detergent compositions with which this invention is concerned normally deepen their initial color when exposed to heat and light. The tendency of our novel compositions to become clearer when exposed to light, therefore runs contrary to all prior experience in this field, and vests in our novel composition a most valuable attribute from the practical viewpoint.

We have further found that the increased clarification or bleaching can be achieved at a much shorter time by exposing our novel composition to an artificial source of actinic light, such as a fluorescent lamp, an ultraviolet lamp, or an ordinary electric light bulb. This accelerated bleaching may not be of a great interest in commercial production, in view of its tendency to increase the cost of the product, but it constitutes a convenient and most valuable means in the laboratory for ascertaining quickly the efficiency of any given additive or mixture of additives to achieve the stabilizing elfect sought after in this invention. Accordingly, this test is used in the specific examples which follow, to bring out the comparative value of the additives and proportions therein discussed.

Inasmuch as many alcohol sulfates are naturally contaminated with iron or acquire iron impurities during their manufacture, we find it suflicient in certain cases to add just citric acid or water-soluble citrates to the detergent. In other cases, iron salts may be added in quantity just sufficient to adjust the total content to the minimum above indicated. In either event, the resulting composition is novel in the sense that it contains at least 4 ingredients, namely (1) water; (2) the active detergent principle, which is the sulfate of a primary alcohol having a longchain alkyl radical, as above defined; (3) citrate ions in concentration of not less than 0.1% to not more than 3% by weight of the entire composition; and (4) metallic ions of the group consisting of iron ions and zinc ions, to a total of not less than 0.0005% and not more than 0.01% by Weight.

The outstanding characteristics of our novel detergent compositions is that they do not deepen their initial coloration upon storage, and that unless their initial coloration has already been destroyed by such a treatment, their color will be improved if aged in daylight or if exposed to an accelerated aging treatment by ultraviolet radiation.

To produce our novel detergent compositions, the mentioned stabilizing agents are simply mixed into the aqueous solution of the alcohol sulfate salt at any convenient temperature.

The requisite citrate ion can be added as the acid or as one of its colorless, water-soluble salts. Any watersoluble salt of iron or zinc is operable, if the accompanying anion is not reactive with any other component of the solution and is not toxic to human beings. Obviously, anions of very high color are to be avoided. Practical illustrations are ferric or ferrous chlorides, nitrates or sulfates, zinc chloride, zinc sulfate and zinc nitrate.

Without limiting this invention, the following examples Ice 2,765,280

3 EXAMPLE 1 The detergent used in this example was a commercial aqueous solution (ab. 33% by weight) of the diethanolamine salt of a monoalkyl sulfate mixture consisting pre dominantly of monododecyl sulfate and containing further the sulfuric acid ester of decyl, tetradecyl, hexadecyl and octadecyl alcohols. A typical composition in weightpercent of the alkyl sulfate mixture is as follows:

Saturated straight chain alcohols Percent Analysis showed this solution to contain about 0.0002% of iron by weight.

To samples of this solution, various proportions of citric acid and ferric chloride were added and dissolved by stirring. A portion of the same solution without added citric acid or ferric ion was retained as a control' The solutions were then placed in 2-02. flint glass vials, capped securely to prevent evaporation, and exposed to the radiation of an ordinary dye-testing fadeometer for a period equivalent to 40 exposure hours.

During the irradiation period, the temperature of the samples reached 160170 F. No noticeable gas evolution occurred and no sediment developed at any stage of the process.

A portion of the control solution was kept in a dark place at room temperature. The exposed samples were then compared visually to the unexposed control to determine any color changes. The following table gives the results observed.

1 Based on solution.

Similar samples containing 0.0025 0.0055%, r 0.0085% ferric ion as ferric chloride with either 1.0%, or 2.0% or 3.0% citric acid gave similar results.

In a third set of samples using the same detergent solution, the materials added prior to aging were:

Zinc ion (Wt.-Percent) Citric acid (Wt-Percent) The samples did not darken on aging, and the bleaching effect of actinic light was even greater than in the samples having a corresponding weight-percent of iron in lieu of zinc.

While the above example emphasizes the use of a carbon-arc fading lamp for obtaining an accelerated aging test, similar results may also be obtained by the use of sunlight through a glass window.

EXAMPLE 2 A commercial aqueous. solution (about wt. of i the triethanolamine salts of the sulfate esters of a commercial lauryl' and oleyl alcohol mixture was used.

A representative composition in weight percent of the oleyl ingredient of this alcohol mixture is as follows:

Saturatei 1Straight: Chain Unsaturated Straight Chain 00 s hols Alcohol Cw 0. 7 1. 1 2. 3 3. 8 4. 3 l6. 0 18. 5 38. 5 l1. 3 3. 5

Wt.-Percent 0f Wt.-Per- Sample No. Ferric Ion in cent of Comparisons vs. Un-

Sample Citric Acid exposed Control I Added 1 control (exposed) severe darkening.

. 0.0025 0. 10 no darkening.

0. 25 considerable bleaching. 1.00 Do. 2.00 Do.

EXAMPLE 3 A commercial aqueous solution (about 27 wt.-percent) of the sodium salt of the sulfate ester of commercial lauryl alcohol was used. (Composition of the alcohol, same as in Example 1.) To samples of this solution citric acid and ferric chloride were added and dissolved by stirring. Portions of the same solution without added citric acid or ferric ion were retained as controls.

The solutions were then aged as in Example 1, with the following results:

Vt-Percent of \VtL-Per- Sample No. Ferric Ion in cent of Comparisons vs. Un-

Sample Citric Acid exposed Control Added control (exposed).. severe darkening. 0.0055 0. 25 considerable bleaching.

1.00 Do. 2. 00 D0.

EXAMPLE 4 The procedure was as in Example 3, except that in lieu of the detergent therein named, anraqueous solution of the mono-sodium sulfate of oleyl-alcohol-ethylene oxide condensation product was employed. This compound is generally prepared by condensing oleyl alcohol with 1 mole of ethylene oxide, then sulfating and neutralizing with sodium hydroxide. The results observed were essentially the same as in Example 3.

In another series of experiments similar tests were carried out upon the sodium sulfates of various condensation products of lauryl alcohol with from 1 to 10 moles of ethylene oxide. The results observed were essentially the same as in Example 3.

EXAMPLE 5 The materials used and procedurewere the same as in Example 3, except that the citric acid in each sample was replaced by an equal weight of sodium citrate. The degree of color change in each sample was found to be essentially the same as in the corresponding sample of Example 3.

EXAMPLE 6 The same detergent as in Example 3 was used, and the same details of procedure, except that the citric acid and ferric chloride in each sample were replaced, on a respectively equal weight basis, by sodium citrate and ferric nitrate. The results observed were respectively the same, as far as could be judged by visual observation.

In several further series of experiments, the iron ion was added, respectively in the form of ferric sulfate, ferrous sulfate, and ferrous chloride. Essentially the same results as in Examples 3 and 4 were observed in each case.

EXAMPLE 7 The detergent used in this series of tests was an aqueous solution (30% by weight) of a diethanolamine monoalkyl sulfate of essentially the same composition as in Example 1. To samples of this solution various quantities of citric acid were added and various quantities of either ferric chloride or zinc chloride. After 40 hours exposure to ultra-violet light from a carbon arc lamp, the following results were observed:

EXAMPLE 8 A sulfation mass prepared by reacting 300 parts of technical lauryl alcohol with 170 parts of chlorosulfonic acid was poured into 1000 parts of aqueous sodium hydroxide solution (6.5%). The resulting alkaline solution of sodium lauryl sulfate, analyzed about 6 p. p. m. of iron, and was light amber in color.

In another experiment, the above procedure was repeated except that 1.45 parts of citric acid were added to the sodium hydroxide solution prior to entry of the sulfation mass. The product thus contained about 0.1% citrate ion, in addition to the 0.0006% of iron ions. In contrast to the product of the preceding paragraph the product of this second experiment was almost colorless and was rated by an expert as having satisfactory clarity. After standing for several weeks in daylight, no noticeable darkening was observed.

It will be understood that the details of the above examples may be varied widely within the skill of those engaged in this art. Thus, in lieu of the specific detergents named in the examples, any detergent of the above general formula may be employed, wherein R and M have the significances above indicated. As common illustrations of suitable water-solubilizing cations coming within the definition of M may be mentioned sodium, potassium, ammonium, or the ammonium radicals corresponding to mono-, dior tri-ethanolamine, morpholine and the like. The concentration of the active ingredient (i. e. the compound of formula RO-SO3M) in the detergent composition may be anywhere from to 80% by weight but is more commonly in the range of 6 to 35% by weight.

It will be clear from the aforegoing that our invention provides novel detergent compositions which are adapted for use in cosmetics and in other fields wherein strictly colorless detergents are required. Furthermore, our invention achieves the above result by the addition of inexpensive stabilizing agents and requires no complicated and costly operations upon the detergent. Finally, because the presence of traces of iron is no longer objectionable in view of our invention, it now becomes possible to use relatively inexpensive and durable, stainless steel equipment in the manufacture of detergents of the alcohol sulfate types, thereby improving the economy of their production.

We claim as our invention:

1. An aqueous detergent composition comprising a principal ingredient and a color stabilizer, the principal ingredient being a compound of the formula wherein M is a water-solubilizing cation, while R-O- is an alcoholic radical of the group consisting of normal aliphatic alcohols of 10 to 20 C-atoms and the condensation products of such alcohols with not more than 10 units of ethylene oxide, and the color stabilizer being a member of the group consisting of citric acid and watersoluble, colorless citrates, the concentration of said principal ingredient being from 6% to 35% by weight of the entire composition, and the concentration of said color stabilizer being from 0.1 to 3% on the same basis, said composition containing further metallic ions of the group consisting of iron and zinc to a concentration of not less than 0.0005% and not more than 0.01% by weight, and being characterized by stability against development of objectionable colors upon storage.

2. An aqueous detergent composition as in claim 1, the principal ingredient being the sodium salt of the monosulfuric ester of a mixture of C10 to C13 saturated alcohols predominating in lauryl alcohol.

3. An aqueous detergent composition as in claim 1, the principal ingredient being the diethanolamine salt of the monosulfuric ester of a mixture of C10 to C18 saturated alcohols predominating in lauryl alcohol.

4. An aqueous detergent composition as in claim 1, the principal ingredient being the sodium salt of the monosulfuric ester of an alcohol mixture obtained by condensing 1 mole of oleyl alcohol with essentially 1 mole of ethylene oxide.

5. An aqueous detergent composition as in claim 1, the principal ingredient being the triethanolamine salt of the monosulfuric ester of a mixture of lauryl and oleyl alcohols.

6. An aqueous detergent composition consisting essentially of water, a detergent, a color stabilizer and a metal salt, said detergent being a compound of the formula wherein M is a water-solubilizing cation, While R() is an alcoholic radical of the group consisting of normal aliphatic alcohols of 10 to 20 C-atoms and the condensation products of such alcohols with not more than 10 units of ethylene oxide, and the color stabilizer being a member of the group consisting of citric acid and watersoluble, colorless citrates, and said metal salt being a member of the group consisting of the chlorides, nitrates and sulfates of zinc, ferrous iron and ferric iron, the concentration of said detergent being from 6 to 35% by weight of the entire composition, the concentration of said color stabilizer being from 0.1 to 3% on the same basis, and the concentration of said metal salt being not less than 0.0005 and not more than 0.01% by weight, said aqueous detergent composition being characterized by stability against development of objectionable colors upon storage.

References Cited in the file of this patent UNITED STATES PATENTS 2,264,103 Tucker Nov. 25, 1941 2,289,004 Franz July 7, 1942 2,674,580 Henkin Apr. 6, 1954 

1. AN AQUEOUS DETERGENT COMPOSITION COMPRISING A PRINCIPAL INGREDIENT AND A COLR STABILIZER, THE PRINCIPAL INGREDIENT BEING A COMPOUND OF THE FORMULA 